Conventional mechanical seal assemblies are used in rotating equipment to provide a seal between regions of high and low fluid pressure and temperature. For example, seal assemblies are used to seal a rotating shaft on a pump, compressor, agitator, gas turbine, or other rotating equipment.
Gas turbine engine type rotational assemblies typically include (in serial flow communication) a fan section, a compressor section, a combustor section, and a turbine section. During operation, air is pressurized in the compressor section and mixed with fuel in the combustor section for generating hot combustion gases. The hot combustion gases flow through the turbine section which extracts energy from the hot combustion gases. In a multiple spool type gas turbine engine, a rotor assembly includes a high speed shaft and a low speed shaft that power the engine components using the energy extracted from the hot combustion gases.
In gas turbine engines, mechanical seal assemblies are used to prevent hot, high pressure air from entering a bearing compartment that operates at a low pressure and temperature. For example, a front bearing compartment in a multiple spool gas turbine engine is filled with an oil mist to lubricate the bearings that support the high speed rotor shaft and the low speed rotor shaft. The high speed rotor shaft and the low speed rotor shaft are separated by a gap filled with working medium gas. The working medium gas cools the rotor shaft. A seal assembly prevents the working medium gas from leaking into the oil compartment and prevents the oil mist from leaking out of the bearing compartment. The seal assembly typically includes a graphitic carbon ring mechanical face seal that seals the bearing compartment. Secondary seals may also be provided to limit leakage.
In order to provide adequate sealing, coil springs are used in the mechanical seal assemblies. Generally, the coil springs rest against a seal housing and compress (or bias axially) the mechanical face seal against the rotating seal seat which rotates with the shaft. However, in order to meet spring load requirements in the seal design, different springs with different compression forces are used and tested. The use of multiple types of springs increases design time, and potentially increasing costs of gas turbine engine hardware.
Accordingly, it is desirable to provide a seal assembly that may decrease design time, and reduce costs of gas turbine engine hardware.